Start the Thieves Guild at level 45+ for the best gear and the Dark Brotherhood can be started immediately. All the best items like the Blade of Woe and Ancient Shrouded aren't leveled so you can get them whenever.
You can find it by traveling South East of Winterhold and North Northeast of Windhelm. The Main entrance is locked and requires a key to open it. The door is unlocked during the quest Speaking With Silence.
Track down the Dunmer behind the Guild's misfortunes. Quest Giver:Mercer Frey Next Quest: Hard Answers Reward: Gallus' Encoded Journal, Word for the Disarm shout ID: TG05 Suggested Level: 62 more rows •
It is recommended that the Dragonborn is at a fairly high level for this quest, preferably level 20 or above.
Send a message to a former Thieves Guild client. Quest Giver:Brynjolf Concurrent Quest: Meet the Family Reward: Leveled gold ID: TG02 Suggested Level: 63 more rows •
Find the books needed to identify the artifact found in Saarthal. Quest Giver:Savos Aren Next Quest: Good Intentions Reward: Skill books ID: MG03 Suggested Level: 82 more rows •
Mercer will inform you that Karliah is hold up inside Snow Veil Sanctum, so lead the way to the door, which Mercer will unlock, and head inside.